It is the one of the most frequently asked questions in portal world and I believe that no one has the right answer. There are various surveys and research reports but all telling different stories. One report is saying that IBM is leading the market and other-one is saying that Plumtree is the market leader. Most of the reports don't consider open source portal servers at all, I don't know why? In my opinion no research can be said complete without including the open source portal servers. Few of my fellow blog authors are of opinion that most of the research reports are fabricated & biased and vendors use them to promote their products only. In my opinion there is no easy method to find the right answer. I have created one survey for finding the answer of the same question. Right now, IBM Portal Server is leading and eXo is at the second spot. Please go and cast your vote. http://groups.yahoo.com/group/portlets/surveys?id=11907382 Note: The poll is on portlets yahoogroup and you need to be the member for casting your vote.